The reason that they release arcade versions first is because in japan arcades are the major gamer gathering spots. Arcades in the states are usually crap and dont pull in as much money because people would much rather sit on their couch and play XBox Live.
So, since their target market is japanese, and the largest market would be the arcades(also due to piracy concerns), arcade releases are the best profit.
Game publishers would make more money if anything if they released directly to PC/console rather than arcades, especially if they set up a digital distribution system for their products. The arcades would die off unless they changed their format (net cafes) but sad fucking story if they don't. Without them, more games would be online and have better net-code and it's not like a lack of arcades = a lack of in-person competitive play. The only reason all this hasn't already happened is because big companies with a shit-ton of management layers are slow to change and often the people making decisions don't understand or properly communicate the factors involved to get anything done. The arcade machine/PCB manufacturers are also invested in not being wiped out so they actively convince their clients that their distribution method is the most viable. It's true that arcades are sustainable in Japan but they're really an inferior place for social/competitive gaming compared to the internet, net cafes and people's houses.